This invention relates to aqueous emulsions of carboxyl-containing silicone fluids, and to a method of making said emulsions. The aqueous emulsions of this invention are substantially more stable than conventional emulsions of carboxyl-containing silicone fluids.
Carboxyl-containing silicone fluids are of recognized utility for a variety of applications, such as for treating textiles to make the textiles softer and more wrinkle resistant; treating human hair to make the hair glossier, softer, and more manageable; and a variety of other uses.
Many of the applications of carboxyl-containing silicone fluids require the deposition of the carboxyl-containing silicone fluid as a thin film upon a surface. Thus, it is customary to furnish the carboxyl-containing silicone fluid as an aqueous emulsion, by which it is meant herein an oil in water emulsion, or solution of the carboxyl-containing silicone fluid in an organic solvent.
Furnishing the carboxyl-containing silicone fluid as an aqueous emulsion has several important advantages over furnishing the carboxyl-containing silicone fluid as a solution. Emulsions are considered more environmentally acceptable than solutions, since the water vapor generated in a drying step is less harmful and/or toxic than vapors of organic solvent generated in a drying step. Additionally, water is less expensive than organic solvent. Finally, aqueous emulsions find particular favor in those applications, such as textile or hair treatment, wherein other treating agents used in conjunction with the carboxyl-containing silicone fluids are themselves furnished as aqueous emulsions or as water soluble salts.
Unfortunately, stability of emulsions is always a problem. With the passage of time, or upon exposure to adverse conditions such as high or low temperatures, aqueous emulsions can degrade: they can cream, i.e. form a thick white layer richer in oil than the bulk of the emulsion; they can oil, i.e. form large droplets or pools of oil; or they can "settle", i.e. liquid water can become separated from the bulk of the emulsion. In the most frequently encountered case of an oil with a lower bulk density than water, creaming and oiling are evident at the surface of the emulsion, and settling is evident at the bottom of the emulsion.
Clearly, creaming, oiling, and settling can lead to unsatisfactory results in the application of the emulsion, such as uneven application of the carboxyl-containing silicone fluid, or they can lead to total disruption of the application process.
U.S. Pat. No. 3,812,201, issued May 21, 1974, discloses an aqueous emulsion of carboxyfunctional polydiorganosiloxane fluid wherein said emulsion is stabilized by a nonionic surfactant consisting of octylphenoxypolyethoxyethanol, said surfactant having approximately ten ethoxy units. While apparently suitable for the use disclosed, similar emulsions are known to be less than satisfactory with respect to stability.
It is generally known in the art that the use of two surfactants rather than just one surfactant can help stabilize an emulsion.
Thus, U.S. Pat. No. 2,755,194, issued July 17, 1956, discloses emulsions of organopolysiloxanes substituted with monovalent hydrocarbon radicals or monovalent, halogenated hydrocarbon radicals, said emulsions being stabilized by trimethylnonylether of polyethylene glycol, a nonionic surfactant, and the sodium salt of an alkylated aryl polyether sulfate, an anionic surfactant.
U.S. Pat. No. 4,246,029, issued Jan. 20, 1981, discloses a coating composition consisting essentially of water, aminorganosiloxane, an organopolysiloxane, and a mixture of two nonionic surfactants. The first of these two nonionic surfactants is octylphenoxypolyethoxyethanol having from 1 to 13 ethoxy units, and the second nonionic surfactant is octylphenoxypolyethoxyethanol having from 6 to 40 ethoxy units.
None of the above references disclose or suggest the compositions of the present invention, which are highly stable aqueous emulsions of carboxyl-containing silicone fluids stabilized by a combination of two particular nonionic surfactants.
Copending U.S. Ser. No. 551,756, now U.S. Pat. No. 4,477,514, assigned to the assignee of the present invention, and entitled "Method For Treating Cellulosic Textile Fabrics with Aqueous Emulsions of Carboxyfunctional Silicone Fluids", describes and claims a method of using some of the compositions of the present invention.